For me, it's most definitely all about the Skyteam general lounge policy and its interpretation. When I'm on an international Skyteam flight (or sameday connection), I expect to have business-class ground service on the basis of my E+ status. If the ST airline I am flying uses a lounge (and I don't care who the lounge belongs to) for C pax, I can get in even when flying in Economy. That's the way it's worked for me dozens of times in tens of different stations across all European ST members, and I expect it to continue if my E+ status is to have any meaning.